Lapping apparatus



March 26, 1940, D. A. WALLACE 2,195,049

' LAPPING APPARATUS Original Filed Nov. 16, 1936 v lfiVENTOR. BY DAVIDA. mqLyncs. M, dam

ATTORNEYS.

Patented Mar. 26, 1940 UNITED STATES PATENT OFFICE LAPPIN G APPARATUSApplication November 16, 1936, Serial No. 111,01 Renewed August 25, 193915 Claims.

This invention relatesto an improved apparatus for lapping surfaces andis a further development of the invention disclosed in my co-pendingapplication Serial No. 91,851 filed 'July 22, 1936.

More particularly, the invention pertains to lapping of surfaces ofapparatus and parts thereof which operate in rubbing, sliding orrotative bearing-like, or frictional contact with other parts.

One of the main objects of the invention is to provide between anarticle being lapped and a lapping element, a relative movement which isa resultant of a plurality of different simultaneous component movementsof the lapping element and the work respectively. 1

Another object of the invention is to produce relative movement of thischaracter between a lapping element and a surface being lapped which isthe resultant of so many components that 20 even during repeatedapplication of the lapping element to the work surface, no isolated areaor particle of the lapping element will be repeatedly applied to thesame increment of area of the work.

A further object of the invention is to provide apparatus for so movingportions of alapping element from one group of machine-formed ridges ofa surface to be lapped to another, during rapid reciprocation of theelement, that the accumu- 30 lated lapped off material and parts of thelapping element which normally tend to foul the working surface thereofare freshly dislodged before advancement of the lapping element tounlapped ridges or ridges in a different stage of the lapping process.

Other objects of the invention are to provide an apparatus for rotatinga piece of work while a surface thereof is in lapping engagement withthe lapping element and simultaneously reciproeating the lapping elementthroughout a relatively short stroke at a rate substantially of avibratory order while also translating the lapping element throughout alonger stroke at a lower speed of movement; to provide lapping elementsof relatively small dimensions and correspondingly light weight inlapping apparatus of this character which are susceptible of convenientreciprocation at high velocity; to provide means for translating suchlapping elements while they are reciprocating, into lapping engagementwith of substantially. greater dimensions than the dimensions of thelapping element; and to provide successively adjacent portions of apiece of work character which reciprocates the lapping elementthroughout a predetermined stroke at one rate of speed while they arealso reciprocated .at a different rate of speed throughout a differentlength of stroke.

Additional objects of the invention are to provide improved means forrotating a piece of Work while it is in operative engagement with thelapping element; to provide means of this character which yieldablysupports and holds the I work in operative engagement with the lappingelement; to provide work supporting and rotating mechanism in apparatusof this kind which will accommodate and properly conditionnoncylindrical surfaces of irregular articles-for the reception oflapping operations of the foregoing character; to provide work holdingmeans of this kind which frictionally rotates the work and which doesnot require that the Work be centered or otherwise conditioned forimparting thereto rotative movement; and to provide work supporting androtating apparatus of this character which will properly position androtate conical and frusto-conical surfaces of pieces ofwork to beoperated upon in accordance with the improved lapping method.

Illustrative embodiments of the invention are shown in the accompanyingdrawing, in which:

Fig. 1 is a fragmentary side elevational view of a lapping apparatusembodying the invention.

Fig. 2 is a fragmentary vertical sectional view taken on the line 22 ofFig. 1.

Fig. 3 is a fragmentary horizontal sectional view taken on the line 3-3of Fig. 1.

Fig. 4 is a fragmentary side elevational view of I -a portion of theapparatus illustrated in Fig. 1

showing a further development thereof.

In the form of the invention illustrated in Figs. 1, 2 and 3, myimproved lapping apparatus comprises a base portion or support It]having a longitudinally extending channel ll provided with an open upperextremity at the top side of the support. Formed on the upper side ofthe support l0, along the lateral edge portions of the channel II, is adovetailed rib l2 on which the carriage l3 of a lapping tool, generallydesignated by the numeral 14, is slidably mounted. The tool carriage I3is provided with a dovetailed groove l5 for receiving-the dovetail rib12, as illustrated in Fig. 2. The tool carriage I3 has an upwardlyextending bifurcated end comprising spaced flanges l6 between which agroove I1 is provided. The tool [4 includes a lever l8 which is disposedin the groove l1 and pivotally supported on the upstanding flanges I6 bya pin I9. Formed in the left end of the lever l8, as viewed a bearing 24carried by the tubular motor casing extension. The motor 22 is securelyheld in place on the lever l8 by a set screw 25 or other suitable means.Slidably mounted in the recess 2| is a block 25 having an apertured lug21 extending downwardly from its lower side. The block 26 is heldagainst displacement from the recess 2| by cleats 28 having edgeportions extending inwardly beyond the edges of the recess and securedto the lower side of the lever I 8 by screws 29.

Pivotally mounted on the apertured lug 21 is a lapping element carrier30, preferably comprising a strip of yieldable and resilient sheet metal3l, on which are attached spaced lapping element brackets 32 ofchannel-shaped cross section. Lapping elements 33, preferably comprisingstones, are securely held in the channelshaped brackets 32. The lappingelements 33 may comprise natural stone, or artificially compressedblocks of lapping material or any other suitable lapping substances. Apivotal coupling member 34 having spaced apertured ears 35 between whichthe apertured lug 21 is receivable. is provided on the upper side of theresilient sheet metal plate 3| for pivotally attaching the lappingelement carrier to the slidable block 26. The

apertured lug 2'Iand apertured ears 35 are pivotally and detachablyconnected together by a removable pin 36 which extends through theapertured lug 21 and ears 35, as illustrated in Fig. 2, the foregoinglapping element mounting and reciprocating mechanism being similar tothat shown in my co-pending application, Serial No. 91,851.

Lapping elements 33 may be drivingly reciprocated by the motor 22 bymeans of an operative connection between the motor shaft 23 and theslidable block 26 which is provided by a pin 31 eccentrically mounted onthe lower extremity of the motor shaft 23 and operatively engaged in anelongated slot 38 formed in and extending transversely of the slideblock 26. During rotation of the motor shaft 23, the slide block 26 isreciprocated at a relatively high speed approaching a speed of avibratory order and in the directions illustrated by the arrow 39 inFig. 3. The stroke of the reciprocatory movement produced by the motor22 is relatively'short but during reciprocation of the lapping elements33 by the motor the entire tool I4 is reciprocated bodily by the slidingmovement accommodated" by the dovetail connection between the support l0and. the tool carriage [3.

Continuous bodily reciprocation of the tool throughout a substantiallygreater length of strokes than that produced by the motor 22 is providedby driving means associated with the support Ill and comprising a crank,generally designated by the numeral 40 in Fig. 2. The crank 40 has abearing portion 4| journaled in an aperture formed in the support H! anda crank throw 42 located in the channel H. Formed on the crank throw 42is a laterally extending crank pin 43,-which is engaged .in asubstantially vertical notch 44 formed: in a downwardly extending flange45 carried by the lower side of the tool carriage l3, as illustrated inFig. 1. The bearing portion 4| has an end part located externally of thesupport ID on which is mounted a pulley 46 which may be drivinglyconnected by a belt or other suitable means (not shown) to a'motor (notshown) or other suitable driving means.

By the foregoing apparatus, the lapping elements 33 are reciprocated ata relatively high speed throughout a comparatively short stroke whilethey also undergo reciprocatory movement of a comparatively longerstroke and at a relatively slower speed. During such reciprocatorymovements of the lapping elements 33, they may be applied to the surfaceto be lapped of an article which is rotatively supported, and preferablydrivingly rotated by any suitable supporting and rotating means.

In the form illustrated in Figs. 1 to 3, inclusive, the work supportingand rotating means, generally designated by the numeral 41, comprises aniaetal base having a substantially horizontal plate 49 provided withspaced upstanding flanges 49 at its respectively opposite ends.Rotatably mounted between the flanges 49 are adjacent rollers 50 havingspaced peripheral portions 5| preferably comprising non-metallicyieldable material having frictional properties, such as rubber. Eachperipheral portion is carried by and preferably bonded to l a centralshaft 52. Opposite end portions of each shaft 52 are journaled inapertures 53 formed in the end flanges 49 of the base plate and one ofthe shafts 52 extends beyond one end flange 49 and is provided with thepulley 54 by whichone roller 50 is directly driven.

A piece of work to be lapped is disposed so as to 'be mutually supportedby both rollers 50 while it is operated upon by the lapping elements 33.In the illustration shown in Figs. 1 and 2, apiston 55 is disclosed inoperative lapping engagement between the rollers 59 and the lappingelements 33. The piston 55 may, as shown in Fig. 2, be of slightlyelliptical or out-ofround contour. During rotation of one of the rollers50, the work 55 is also rotated and in turn drives the other roller 50.If desired, the rollers may be drivingly connected together by suitablegearing (not shown) including an idler pinion by which the rotativedrive may be imparted directly from one roller to another while stillmaintaining rotation of the rollers in the same direction.

The lapping tool l4 may be rotated in a counterclockwise direction, asviewed in Fig. 2, about the pivot l9 in order to accommodate removalviewed in Fig. 2. Adjustably mounted on the stem 56 is a counter-balanceweight 51 which may be releasably held in an adjusted position by a setscrew 58. The balance weight 51 is adjustably positioned so as tocounter-balance all but a desired portion of the moment of the motor andportion of lever l8 on the right hand side of the pivot I9 in order topredetermine the force by which thelapping elements 33 are applied tothe surface operated upon.

In the form of the invention illustrated in Fig. 4, there is provided apair of frusto-conical shaped rollers 50' each comprising an outeryieldable peripheral portion 5| formed of non-metallic, yieldable,frictional material, preferably comprising rubber, and a-central shaft52'. Each rectly drivingly rotated. The rollers 50 are arranged inadjacent relationship in the manner illustrated in Fig, 2 and they areadapted to mutually support a frusto-conical shaped piece of work 59 asshown in Fig. 4. The frusto-conical rollers 50' may be mutually directlydriven by gear mechanism (not shown) including an idler gear interposedtherebetween in order to drivev both rollers in the same direction. Inthe form shown, however, the rotatively driven roller rotates the workand the latter,-in turn, rotates the other roller.- The inclinations ofthe sides of the rollers 50' are preferably so predetermined withrespect to the inclinations of the sides of the work 59 as to bring theuppermost extremity thereof, represented by the line 60 in Fig. 4, intoa substantially horizontal position in order that the surface of thework may be properly presented to the lapping elements 33.

By virtue of the foregoing lapping apparatus and method the relativemovement produced-between the work and the lapping element is aresultant of a plurality of different components which assures removalof the machining formed ridges of the surface operating upon withoutproducing scratches by repeatedly bringing isolated portions, or hardparticles of the lapping surface of the lapping element into repeatedengagement with the same increment of area of the work. Relatively smalland light lapping elements may be used upon work having surfaces of muchgreater dimension while assuring equal application of the lappingelements to all portions of the work surface. This is accomplished bynot only reciprocating the lapping elements relative to the lappingtool, but by bodily reciprocating the lapping tool through substantiallylong strokes at a comparatively slow speed. The combined reciprocationsof the lapping elements at relatively high speed throughout acomparatively short stroke, assures removal of metal and particles ofthe lapping element from between the grains of the latter at its workingsurface and thereby maintains the working surface of a lapping elementin a clean and efficient cutting condition.

The yieldable work supporting and rotatin apparatus facilitates rapidand ready removal of work from the machine and placement of work thereonand accommodates articles of non-cylindrical shape. By frictionallydriving the work in the foregoing manner, the requirements of centeringthe'work is dispensed with as well as are the hazards of injuring thework during mounting thereof for rotation about a fixed center. Byyieldably supporting the work in this manner, the surfaces ofout-of-round articles, such as elliptical pistons, may, be lapped to ahigh degree of smoothness substantially without varying their dimensionsand contours and particularly without excessively removing metal fromthose portions ofthe work which are located at greatest distance fromits central axis.

Although several specific embodiments of the invention are herein shownand described, it will be understood that various changes in the size,shape and arrangement of parts may be made without departing from thespirit of my invention.

What I claim is:

1. Lapping apparatus comprising a support, means adjacent said supportfor rotatably supporting a piece of work, a lapping tool shiftablymounted on said support for movement in the general direction of theaxis of said work including a main body part having an end portionadjacent saidwork and a'reciprocable lapping element and holderassembly, said assembly constituting only a small portion of the mass ofsaid tool and being movable in said direction relatively to said lappingtool and engageable with said work, mechanism for rotating said work andreciprocating said tool bodily relative to said support at a comparativeslow speed, and driving mechanism on said tool for reciprocating saidlapping element relative thereto at a substantially faster rate ofspeed.

2. Lapping apparatus comprising a support, means adjacent said supportfor rotatably supporting a piece of work, a lapping tool including abody portion shiftably mounted on said support and a lapping element andholder assembly, said assembly being many times lighter in weight thanthe main body portion of said tool and being reciprocable relative tosaid body portion in a direction substantially parallel to the rotativeaxis of said work at a speed of a vibratory order and said lappingelement being engageable with said work, a driving member on said toolconstructed and arranged to reciprocate said lapping element relative tosaid tool body portion throughout a relatively short stroke and at acomparatively high speed of a vibratory order, mechanism for rotatingsaid work, and apparatus for reciprocating said tool bodily relative tosaid support throughout a substantially longer stroke and at acomparatively slower rate of speed.

3. Lapping apparatus comprising a support and having a guide memberthereon, means adjacent said support for rotatably supporting a piece ofwork, a lapping tool having a body portion shiftably mounted at one endon said support and confined by said guide member to shifting movementsin a path substantially parallel to the rotative axis of said work andhaving an opposite end portion extending over said work, said toolcomprising a lapping element reciprocably mounted on the latter endportion of said body portion, and means for confining the reciprocatingmovement of said lapping to a path substantially parallel to said axis.a driving member on said tool constructed and arranged to reciprocatesaid lapping element relative thereto throughout a relatively shortstroke and at a comparatively high speed, mechanism for rotating saidwork, and apparatus for reciprocating said tool bodily relative to saidsupport throughout a substantially longer stroke and at a comparativelyslower rate of speed.

4. Lappingapparatus comprising a support, means adjacent said supportfor rotatably sunporting a piece of work, a tool carrier shiftablymounted on said support, a lapping tool pivotally mounted on said toolcarrier having an end portion registering with work supported by saidmeans, a lapping element reciprocably mounted on said end portion ofsaid tool and engageable with work supported by said means. a" drivingmember mounted on said end portion of said tool for reciprocating saidlapping element and urging the same toward said work, and mechanism fordriving said work rotating means and reciprocating said tool bodilyrelative to said support.

5. Lapping apparatus comprising a support, means adjacent said supportfor rotatably supporting a piece of work, a tool carrier shiftablymounted on said support, a lapping tool pivotally mounted on said toolcarrier having an end portion registering with work supported by saidmeans, a lapping element reciprocably mounted on said end portion ofsaid tool and engageable with work supported by said means, a drivingmember mounted on said end portion of said tool for reciprocating saidlapping element and urging the same toward said work, mechanism fordriving said work rotating means and reciprocating said tool bodilyrelative to said support, and means carried by said tool on the oppositeside of the axis of the pivotal mounting thereof from that on which saidlapping element is located for counterbalancing selected portions of theweight of said driving member to predetermine the pressure ofapplication of said lapping element upon said work.

6. Lapping apparatus including means for yieldably supporting andfrictionally rotating a piece of work, a lapping tool comprising alapping element reciprocably mounted thereon and adapted to bear uponand urge work supported by said means toward the latter, and mechanismfor driving said means to rotate said work and for drivinglyreciprocating said lapping element re spectively.

7. Lapping apparatus including means for yieldably supporting andfrictionally rotating a piece of work, a lapping tool comprising alapping element adapted to bear upon and urge work supported by saidmeans toward the latter, and mechanism for driving said means to rotatesaid work.

8. Lapping apparatus including means for yieldably supporting andfrictionally rotating a piece of work having generally circular crosssections by engagement with the surface of said work to be lapped, alapping tool adjacent said means having a lapping element engageablewith said surface and adapted to bear thereon in the direction of saidyieldable supporting means, and mechanism for driving said means torotate said work.

9. Lapping apparatus including means for yieldably supporting andfrictionally rotating 2. piece of work having generally circular crosssections by engagement with the surface of said work to be lapped, alapping tool adjacent said means having a reciprocable lapping elementengageable with said surface and adapted to bear thereon in thedirection of said yieldable supporting means, a member on said tool fordrivingly reciprocating said lapping element while the latter is inengagement with said surface, and mechanism for driving said means tosimultaneously rotate said work.

10. Lapping apparatus including means for yieldably supporting andfrictionally rotating a piece of work comprising a pair of adjacentrollers having yieldable peripheral portions between portions of whichsaid work is receivable, a support adjacent said means, a lapping toolcarried piece of work comprising a pair of adjacent rollers havingyieldable peripheral portions between portions of which said work isreceivable, a support adjacent said means, a lapping tool carried bysaid support and comprising a reciprocable lapping element engageablewith said work and adapted to bear thereon in the direction of saidmeans, a member mounted on said tool for drivingly reciprocating saidlapping element, and mechanism for driving said rollers to rotate saidWork.

12. Lapping apparatus including means for yieldably supporting andfrictionally rotating conical and frusto-conical articles comprising apair of frusto-conical rolls having yieldable peripheral portions, saidrolls being so constructed as to bring the periphery of one of saidarticles into substantially parallel relationship with respect to saidrolls at the side of said articles remote from said rolls when saidarticle is supported thereon, a lapping tool comprising a lappingelement reciprocably mounted thereon and confined for reciprocation indirections substantially parallel to the axis of said rolls, saidlapping element being engageable with the portions of the periphery ofsaid article which are substantially parallel with said axis, andmechanism for simultaneously drivingly reciprocating said lappingelement and rotating said article.

13. Lapping apparatus comprising a support, means adjacent said supportfor rotatably supporting a piece of work, a lapping tool shiftablymounted on said support including a main body portion and a lappingelement and holder assembly, said lapping element being engageable withsaid work and said assembly constituting only 'a substantially smallportion of said tool as compared to said main body portion and beingreciprocable relative to said main body portion in a directionsubstantially parallel to the axis of said work, and apparatus fordrivingly rotating said work, reciprocating said lapping elementassembly relative to said main body portion of said tool andreciprocating said tool relative to said support simultaneously.

14. Lapping apparatus comprising a support and having a guide memberthereon, means adjacent said support for rotatably suporting a piece ofwork, a lapping tool shiftably mounted on said support and confined bysaid guide member to shifting movements in a path substantially parallelto the rotative axis of said work, said tool comprising a main bodyportion and a lapping element and holder assembly, said assemblyconstituting only a substantially small portion of the mass of said toolas compared to the main body portion thereof and being reciprocablerelative thereto in a path substantially parallel to said axis, andseparate and independent driving mechanisms for individually drivinglyrotating said work, reciprocating said lapping element relative to saidmain body portion of said tool and reciprocating said tool relative tosaid support respectively.

15. Centerless lapping apparatus comprising a support, a tool carriermember mounted on sa d support, a work supporting member adjacent saidsupport including a roll for rotatably supporting and frictionallyrotating 9. piece of Work, a lever mounted at one end portion of saidtool carrier member and having an end portion registering with saidwork, said registering end portion of said lever having a lappingelement and holder assembly reciprocably mounted thereon, said lappingelement and bolder assembly comprising a relatively small mass ascompared to the mass oi said lever and tool carrier member, said lappingelement being engageable with work supported by said work supportingmember, said work supporting and tool carrying members being relativelyreciprocable, a driving member for producing relative reciprocation ofsaid members,

means entirely independent of said driving member for drivinglyreciprocating said lapping element relatively to said tool carriermember, and mechanism entirely independent of said aforesaid drivingmeans and member for drivingly rotating said roll to rotate said work.

DAVID A. WALLACE.

